Given two relations Ri and R2, where Ri contains Ni tuples, R2 contains N2 tuples, and N2> Ni> 0, give the minimum and maximum possible sizes (in tuples) for the resulting relation produced by each of the following relational algebra expressions. In each case, state assumptions about the schema for R and R2 needed to make the expression meaningful: 1. Ri U R2 2. Ri - R2 3. a_5(RI); 4. Tta(R1)